Recent years, heat exchanger type ventilating fans effective in saving energy have been popular. A heat exchanger for exchanging heat between indoor and outdoor air can save energy in an air conditioning device by recovering heat lost during ventilation of indoor air. An example of a counter flow system heat exchanger is disclosed in Unexamined Japanese Utility Model Publication No. 1981-89585.
Hereinafter, a description is provided of the conventional heat exchanger with reference to FIGS. 30 through 32.
As shown in FIG. 30, L-shaped spacers 102, each protruding so that the backside thereof is recessed to have a substantially V-shaped section, are formed on the surface of heat conduction plate 101 made of a plastic material, such as a rigid vinyl sheet.
A plurality of spacers 102 are spaced with each other to form heat conduction plane 103. The periphery of heat conduction plate 101 forms bent edges 104 that open slightly outward of the plane perpendicular to the plate.
At both ends of spacers 102 and along the outside halves of bent edges 104a and 104b facing the ends, slots 105a and 105b are provided as air inlets and outlets, respectively. Additionally, along the inside halves of the other bent edges 104c and 104d, slots 105c and 105d are provided as the air inlets and outlets symmetrically with slots 105a and 105b formed along the outside halves, respectively.
Then, laminating a plurality of heat conduction plates 101 so as to be positioned in orientations 180 degrees different from each other in one plane provides heat exchanger 106 as shown in FIG. 31.
As shown in FIG. 32, spacers 102 on heat conduction plate 101 and spacers 102 on adjacent heat conduction plate 101 are positioned parallel but misaligned to each other so as not to overlap. In this manner, the apexes of spacers 102 on a heat conduction plate are in contact with the top surface of heat conduction plane 103 of the adjacent heat conduction plate, and the outside half of bent edge 104 overlaps the inside half of adjacent bent edge 104. Thus, two kinds of air channels 107a and 107b divided into a plurality of L-shaped air ducts by spacers 102 are alternately formed between these heat conduction plates 101. At one end of each channel, slots 105a or 105c in the bent edges form inlets. At the other end of each channel, slots 105b or 105d in the bent edges form outlets, in the similar manner.
The arrows in FIG. 32 show fluid flows.
In the above conventional heat exchanger, no air flows through the portion of spacer 102 having substantially a V-shaped section. For this reason, in the portion in which apex W of spacer 102 is in contact with heat conduction plane 103 of heat conduction plate 101, no heat is exchanged. Reducing the area of apex W by substantially V-shaping the section of spacer 102 intends to reduce the area in which no heat is exchanged. However, spacers 102 on heat conduction plate 101 and spacers 102 on adjacent heat conduction plate 101 are positioned parallel but misaligned to each other not to overlap, and apexes W of spacers 102 are in contact with the top surface of heat conduction plane 103 on the adjacent heat conduction plate. This structure doubles the portion of no heat exchange on heat conduction plate 101 and heat conduction plate 101 under the former plate.
As a result, this structure poses a problem that reduction in effective heat transfer area deteriorates heat exchange efficiency. Thus, increases in the heat transfer efficiency are required.
Additionally, in heat exchanger 106 obtained by laminating a plurality of heat conduction plates 101 in orientations 180 degrees different from each other in one plane, only spacers 102 support the spacing between heat conduction plates 101.
For this reason, weight of the plurality of laminated heat conduction plates 101 or external force exerted thereon can deform spacers 102 and air channels 107a and 107b can collapse. This poses a problem of decreasing the opening areas of the channels and increasing pressure loss. Thus, improvement of strength and reduction in pressure loss are required.
Heat conduction plate 101 is obtained by vacuum-molding a plastic material, such as a rigid vinyl sheet, and cutting five portions, i.e. the outer periphery of bent edges 104 and slots 105a, 105b, 105c, and 105d in the bent edges. At this time, it is difficult to cut out the outer periphery of bent edges 104 in a vertical direction and four slots in the bent edges in a horizontal direction by one step. This poses a problem of low production efficiency, and thus improvement thereof is required.
In the outer peripheries near the inlets and outlets of heat exchanger 106, because bent edges 104 of heat conduction plate 101 are in contact with spacers 102 on another heat conduction plate 101 laminated thereon, spacers 102 prevent bent edges 104 from being deformed by lateral external force. Thus, air-tightness is unlikely to be deteriorated by deformation of bent edges 104.
However, the outer peripheries in the portions other than the inlets or outlets in heat exchanger 106 only has contact of bent edges 104 of heat conduction plate 101 with bent edges 104 of another heat conduction plate 101 laminated thereon. Thus, bent edges 104 are likely to be deformed by lateral external force. This poses a problem that deformation of bent edges 104 deteriorates air-tightness. Thus, improvement of strength and a highly air-tight structure are required.
The present invention aims to address these conventional problems, and provides a heat exchanger having improved basic performance, such as increasing heat exchange efficiency and decreasing pressure loss, as well as improved productivity and strength.